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Bug #34294 Bug in casting a float to integer
Submitted: 2005-08-29 13:35 UTC Modified: 2005-09-22 21:37 UTC
From: moerel at gmail dot com Assigned:
Status: Not a bug Package: Math related
PHP Version: 5.0.4 OS: Linux
Private report: No CVE-ID: None
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From: moerel at gmail dot com
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 [2005-08-29 13:35 UTC] moerel at gmail dot com 
Description:
------------
I found some strange behaviour while casting a float to integer. It looks like something gets rounded in a strange way while casting.



Reproduce code:
---------------
<?
	$fltTest = 9.95;

	print ($fltTest * 100) . '<BR>';
	print round($fltTest * 100) . '<BR>';
	print (int)($fltTest * 100) . '<BR>';
?>


Expected result:
----------------
995
995
995


Actual result:
--------------
995
995
994

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 [2005-08-29 13:41 UTC] sniper@php.net 
Floating point values have a limited precision. Hence a value might 
not have the same string representation after any processing. That also
includes writing a floating point value in your script and directly 
printing it without any mathematical operations.

If you would like to know more about "floats" and what IEEE
754 is read this:
http://docs.sun.com/source/806-3568/ncg_goldberg.html
 
Thank you for your interest in PHP.
 
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